Add groups option to cluster proxy (#297)

This change adds an option to specify groups a cluster proxy peer is a
member of.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added optional `spec.groups` to the ClusterProxy custom resource to
associate group references by `id`, `name`, or `localRef`.
* CRD schema includes OpenAPI validation to enforce that each group
reference specifies exactly one selector.

* **Bug Fixes**
* Improved deep-copy behavior for ClusterProxy spec so group references
are copied safely and don’t share underlying slices.

* **Documentation**
* Updated API reference docs and README API table to include the new
`groups` field.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

api/v1alpha1/zz_generated.deepcopy.go

@@ -17,7 +17,7 @@ func (in *ClusterProxy) DeepCopyInto(out *ClusterProxy) {
 	*out = *in
 	out.TypeMeta = in.TypeMeta
 	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
-	out.Spec = in.Spec
+	in.Spec.DeepCopyInto(&out.Spec)
 	in.Status.DeepCopyInto(&out.Status)
 }
 
@@ -74,6 +74,13 @@ func (in *ClusterProxyList) DeepCopyObject() runtime.Object {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *ClusterProxySpec) DeepCopyInto(out *ClusterProxySpec) {
 	*out = *in
+	if in.Groups != nil {
+		in, out := &in.Groups, &out.Groups
+		*out = make([]GroupReference, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ClusterProxySpec.